1. Field of the Invention
The present invention relates to a clamp apparatus capable of clamping a workpiece which is positioned on a carriage and transported in an automatic assembly line.
2. Description of the Related Art
Workpieces of engines are transported by carriages, for example, in automatic assembly lines for manufacturing automobiles. A variety of machining steps and assembling steps are performed at respective stations.
At each of the stations, it is necessary to position the workpiece in order to fix on a jig. Recently, a clamp apparatus is provided on the carriage itself. The workpiece is transported while clamped on the carriage. Only the carriage is positioned at each of the stations.
In this system, for example, a rotary driving source such as a motor is used as a driving source for the clamp apparatus.
In the clamp apparatus, the rotary driving source produces the rotary driving force which is transmitted to a ball screw by a gear mechanism. The rotary driving source is provided integrally with a body and is driven by an electric signal. The rotary driving force is converted into the rectilinear motion of the ball screw which is displaceable in the axial direction in accordance with the rotation in the body. The rectilinear motion of the ball screw is transmitted to a toggle link mechanism by a knuckle joint. A clamp arm is rotated by the rotary action of a support lever of the toggle link mechanism so that the workpiece is clamped. Accordingly, the clamping force of the clamp arm is applied by the rotary driving force of the rotary driving source (see, for example, Japanese Laid-Open Patent Publication No. 2001-310225).
In the conventional clamp apparatus, the driving force produced only by the rotary driving source is used to displace the ball screw rectilinearly by rotating the gear mechanism, to transmit the driving force to the toggle link mechanism through the knuckle joint by the displacement of the ball screw, and to rotate the clamp arm for clamping the workpiece by rotating the support lever of the toggle link mechanism. Therefore, a large driving load may be exerted on the rotary driving source. In other words, the driving load exerted on the rotary driving source is large, because all of the motions of the components depend on the driving force of the rotary driving source.
The gear mechanism comprises a plurality of gears which are meshed with each other, for transmitting the rotary driving force of the rotary driving source to the ball screw. Therefore, the body, in which the gear mechanism is accommodated, tends to be large in width. For this reason, it is preferable if the entire apparatus is miniaturized by decreasing the width of the body.
Further, the conventional clamp apparatus requires, for example, a DC power source or an AC power source for supplying the DC or AC current in order to drive the rotary driving source. It is sometimes difficult to install the DC power source or the AC power source depending on the environment of use of the clamp apparatus.
Further, in the conventional clamp apparatus, wiring operation to connect the rotary driving source to the DC power source or the AC power source is complicated even when the DC power source or the AC power source can be installed in the environment.